When I disconnected my backup drive and plugged in a USB drive the other night, my Windows drive letters got all wonky. D: became G: became F: became H:, and a bunch of my shortcuts didn't work anymore.

But it's easy to reassign the drive letters of your choice to add-on disks in Windows. Microsoft says you should log on as an administrator, and from Administrative Tools in Control Panel:

Double-click Computer Management, and then click Disk Management in the left pane.

Right-click the drive, the partition, the logical drive, or the volume that you want to assign a drive letter to, and then click Change Drive Letter and Paths.

Of course things can get wacky if the disk is in use - by your computer or another on the network - so proceed with caution, you drive alphabetizer, you.